Acetic acid, as one of fundamental chemicals, is a significant chemical to be widely used in the petro-chemistry; polymer chemistry; organic chemistry; medicine; and pesticide fields. Among variously known methods of production of acetic acid, particularly useful is the preparation of acetic acid by a carbonylation of methanol using carbon monoxide.
Conventional methods of preparing acetic acid by a carbonylation of methanol include: 1) a Monsanto process where rhodium (Rh) commercialized in the 1960s [Patent Document 1] is mostly employed; 2) a Cativa process for which iridium (Ir) commercialized in the 1990s [Patent Documents 2 to 4] is usually used; and 3) an Acetica process using a heterogeneous catalyst, to fix a rhodium (Rh) catalyst fixed on a polymer [Patent Documents 5 to 7]. Although the above processes are satisfactory with regard to reactant conversion and selectivity, they suffer from waste of energy, i.e. a large amount of energy is required for each process of catalyst recycling and the byproduct treatment. In particular, the Monsanto and Cativa processes using the homogeneous catalyst, in which the expense of catalyst recycling is very large, are considered unprofitable at present, and the Acetica process using the heterogeneous catalyst is getting a great deal of attention, and thus, there are increasing research reports relating thereto.
Taking it into consideration that a carbonylation reaction of methanol is carried out in a liquid state, the Acetica process has an advantage of minimizing the loss of the catalyst due to the fixation of the rhodium precious metal on the polymer support. However, with regard to the heterogeneous catalytic reaction using the polymer support, it has been reported that the activity of the catalyst is slightly decreased compared to the homogenous catalytic reaction. Recently, the use of a support having a structure of activated carbon or hydrotalcite in lieu of the polymer support has been proposed. [Patent Document 8]
Also, thorough research is ongoing into minimizing the loss of rhodium precious metal and controlling the interaction between the rhodium active component and the support to thus increase the stability and dispersibility of the catalyst. In this regard, Non-Patent Document 1 discloses a technique for fixing, on the support, a rhodium complex using 3-benzoylpyridine as a functional group for optimizing the rhodium-support interaction.